1. Field of the Invention
The present invention relates to an optical encoder and a bending operation system configured to detect a longitudinal displacement of a linear power transmission member such as a wire, and to a method of detecting a displacement of the linear power transmission member using the optical encoder.
2. Description of the Related Art
In general, operation systems, for example, a manipulator and an endoscope use a driving mechanism configured to bend a moving part by a linear power transmission member such as a wire. These operation systems need to be provided with a detecting mechanism configured to detect the bending angle of the moving part in order to accurately control the movement of the endoscope and manipulator.
An encoder that uses an optical fiber has been disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-18971. In this encoder, light enters a target rotor from a light source via the optical fiber, and the amount of the light reflected to the optical fiber from the rotor is detected. Thereby, the rotation position and rotation direction of the rotor are detected.
Published Japanese Patent No. 4005318 discloses an optical fiber type detection sensor configured to detect the bending angle of an endoscope. In this detection sensor, a plurality of light absorbing parts are formed in the optical fiber, and the amount of light absorbed by the light absorbing parts is detected. The amount of light absorbed by the light absorbing parts changes depending on the bending angle of a moving part of the endoscope. Therefore the amount of light absorbed by the light absorbing parts is detected to detect the bending angle of the moving part of the endoscope.